Patent GB-650765-A (GB)
Title: Improvements in artists' brushes
IPC: A46B3/12
Filed: 1946-11-21
Abstract: 650,765. Artist's brushes: bristle fixing ; shaping brush-heads by grinding SHAW, C. K. Nov. 21, 1946, No. 34592. [Classes 19 and 60] A process of manufacturing artists' brushes having as bristles, filaments of nylon or other synthetic resin is characterized in that the brush is subjected to a grinding operation during which the bristles are prevented from splaying out and whereby the brush-head is fashioned to a desired pointed or chisel-edged shape, and is then subjected to a further grinding operation during which, by hand manipulation of the brush, the bristles are splayed out on the abrasive surface while both rotating or oscillating the brush-head and varying the length of filament in contact with the abrasive surface. The process provides artist's brushes of desired shape with the individual bristles tapered. Conveniently a double-purpose grinding jig may be utilized. As shown, Fig. 5, this jig comprises a base-plate 7 which slidably engages the grinding table 8 of a rotary grinder having an emery-faced disc 9, the jig being positioned by clamping screws 10. The right-hand half of the jig is adapted for the preliminary grinding; the baseplate 7 has an integral extension 7a, Fig. 8, to which are cemented segments 11 spaced apart to provide channels for different widths of brush and maintained rigid by a strip 12. The brush is positioned as shown, and rotated if a pointed end is required or ground on one side and then turned over and ground on the other side to form a chisel-edge, the segments 11 preventing lateral spread. The left-hand half of the jig is utilized in the final grinding; to this end a strip 14, supported by a bracket 13, is spaced a little distance away from the face of grinding disc 9 so that the bottom edge of strip 14 is disposed at a slight angle to the disc face leaving a gap F, Fig. 7, which tapers towards the disc centre. The pointed or chisel-edged brush-head is inserted under, the strip 14 and since there is no lateral control, the bristles spread out on the grinding surface whereupon the brush is oscillated with the fingers and moved to-and-fro sideways across the face of the grinding disc. In this way, through the tapering of the gap, the length of bristles drawn into the gap F by the rotating disc and the abrading pressure of the bristles on the disc are varied and the operator is enabled to give the bristles the desired taper. The complete jig is preferably made of " Perspex " (Registered Trade Mark) so that the work may be seen throughout the process. The brushes to be ground may be assembled by laying out a combed bundle of long nylon threads in a knotting jig 1, Fig. 1, which may also be of " Perspex " or metal, provided with saw cuts 2 into which have been laid knotting threads 3; these threads are tied round the bundle and the bundle then cut up into tied knots which are mounted in ferrules in the usual manner, preferably using a urea or phenol-formaldehyde cement. A wide brush may be made in the same way by tieing a plurality of bundles one above the other by the same knotting threads, and a flattened ferrule is used. Flat brushes may be formed from a single bunch by using a slightly large ferrule which is subsequently flattened about the bunch. Alternatively, the brushes may be assembled by charging a cup-mould with ready cut filaments, tieing the bunch and then transferring it to the ferrule as before. The brush may have a central core of thick filaments surrounded by thin ones which may themselves be surrounded by thinner filaments. According to the Provisional Specification, the grinding process may be effected by means of a power-driven belt faced with glass paper or emery cloth the bristles being held against the abrasive at an angle and at the same time slowly rotated in the fingers to ensure that each filament, and each side of it comes into contact with the abrasive; a knot may be so ground and then secured in a ferrule.